Prior art streetlights have typically used high pressure mercury lamps, sodium lamps, metal halide lamps, and induction lamps. These lamps have worked well in the field proving to be bright and reasonably reliable. Each of the abovementioned types suffers to a greater or lesser degree from the following disadvantages. The prior art lamps have a strong tendency to scatter light in all directions. Thus, high power consumption is required to maintain a desirable degree of luminescence on the ground where the light is needed.
Recently, LED street lamps have begun to replace older styles of lamps because LED lamps are able to produce light output equal or greater than that of conventional mercury, sodium and induction lamps and the output is substantially more directional, i.e. the light output suffers from significantly less scatter. In addition, LED lamps consume substantially less power than older types of lamps and are capable of having a much longer service life.
LEDs also have certain drawbacks. In particular, the high level of luminescence required in a street lamp cannot be met by the use of a single light emitting diode. In order to achieve luminescence comparable to mercury, sodium, or induction street lamps, numerous LEDs are required to be packaged in a single light housing. For example, a plurality of LEDs may be arranged on a circuit board (module) in a series or parallel circuit and several such boards or modules may be incorporated in a single lamp housing.
When LED lighting systems comprising modules composed of a plurality of light emitting diodes are turned “on” for long periods of time, however, they tend to generate a substantial amount of heat. LEDs are well known to be sensitive to heat. An excessive amount of heat, over a long period of time, may cause the structures forming the LED module to fail or to deteriorate and therefore negatively affect the brightness and service life of the LED lamp. LEDs are prone to heat related failures because the circuit boards to which they are mounted are generally poor conductors of heat. It is now common for LED lamps intended for lighting public areas to operate within the range of 50 to 300 watts. Operation at such wattage levels is sufficient to degrade the individual LEDs which make of modules contained in the lamp unless adequate cooling is provided.
Accordingly, there is a need in the art for streetlamp housings which include cooling structures to dissipate the heat generated from the LEDs. There is also a need in cold weather climates to prevent ice from forming around and bridging the AC contacts found within a streetlamp.